Coffee lovers everywhere agree that espresso is one of the most delicious drinks out there. But what’s often overlooked is the science behind it: how many bars of pressure for espresso?
Here, I’m going to show you the science behind a great espresso shot, and how many bars of pressure are usually needed for making a quality cup…
What is the Ideal Pressure for Espresso?
When it comes to making the perfect espresso, pressure has a key role to play. But how much pressure is necessary for the perfect cup?
Well, it’s widely accepted that 9 bars are the sweet spot for espresso. To put this into context, atmospheric pressure (at sea level) is 1 bar, a car tyre has 2 – 3 bars and a scuba tank holds up to 200 bars. So 9 is pretty impressive.
To achieve this optimal level of pressure it’s important to use an espresso machine with a suitable pump. The pump should run steadily and consistently, applying even pressure throughout the entire brewing process.
Why 9 Bars of Pressure Is an Ideal Measure for Espresso?
Have you ever wondered why 9 bars of pressure are the ideal measure for creating the perfect espresso? I know I certainly have! Through my research, I have discovered many reasons why 9 bars are the optimal amount.
Firstly, the way espresso is made requires putting hot water in a portafilter and compressing the ground coffee with a high-pressure pump. This process, called ‘tamping’, typically requires a pressure of between 8 and 10 bars to ensure that the ground coffee is properly compressed.
Secondly, using 9 bars of pressure draws out natural oils from coffee beans which help enhance your espresso’s flavour notes and provide that signature crema on top. This crema is essential for making velvety micro-foam.
Finally, to consistently achieve good quality and flavour in every cup of espresso, it’s important to use a consistent level of pressure throughout each extraction process – 9 bars being an ideal measure as it’s easy to keep stable even with regular use.
Types of Espresso Machines and Their Pressure Levels:
Espresso machines come in various shapes and sizes, each having different levels of pressure. Generally, the more expensive the machine, the higher the level of pressure it has. Let’s take a look at the three main types of espresso machines and what kind of pressure they bring to the table.
Pump Espressos: These machines are probably one of the most common espresso makers out there. Different models range from between 8 and 15 bars, although many older models will have even lower levels.
Manual Lever Espressos: These machines require skill and practice, as different levels of pressure will yield different results – depending on how hard you press down on that lever!
Stovetop Espressos: These machines use heat from your stove to force hot water up through ground coffee beans at a much lower 2-3 bar level than electric models; making it easier to achieve an espresso with crema on top.
How to Create a Consistent Flow Rate for Espresso Extraction?
Brewing espresso is, fundamentally, a science. It requires a precise combination of heat, pressure and time in order to effectively extract the coffee solubles.
While it’s important to understand the basics of brewing espresso, you’ll also need to be mindful of some other considerations when creating a consistent flow rate. Here are a few tips that I’ve learned over the years:
Getting your temperature right is essential when making espresso. You’ll want to aim for around 200°F (+/- two degrees). Any colder and your coffee won’t be extracted properly. Too hot and you run the risk of it burning your grounds and producing an unpleasant flavor.
2. Time Tracking:
You should always track how long it takes for your espresso extraction. This way, you can ensure that the same amount of time passes each time you brew an espresso shot. You don’t want your shots to vary in length—aim for about 25 seconds for a single shot (1 oz) or 45 seconds for a double (2 oz).
3. Pressure and Grind Size:
Your grind size needs to be just right — if it’s too coarse, then water will pass through too quickly; if it’s too fine, then water will pass through slowly. The ideal grind size should allow water to travel through at nine bars of pressure. This is considered optimal as it allows enough pressure to penetrate the grounds while also avoiding any over-extraction or bitterness in the cup.
What are Common Pressure-Related Issues?
The answer is actually quite complex, as the pressure used to brew an espresso shot can be one of a few different sources and can vary from machine to machine.
1. Human Factor:
First off, it’s important to understand that the human factor plays a role in the pressure used for espresso shots. A barista with the technical expertise and feel for their machine can use more or less pressure than indicated on the machine’s settings for optimal extraction time. This takes considerable practice but can be done with great results.
2. Lever vs. Pump machines:
Another key factor is the type of espresso machine you are using; manual lever machines flavour shots differently than pump machines as they usually require more force (higher pressure) to extract espresso. This means that if you’re using a lever machine, you may want to use higher pressure than what is displayed on your settings.
3. Pressure gage readings:
Finally, some machines are equipped with a built-in pressure gauge that provides an indication of how much steam is entering your portafilter basket while pulling your shots. While these aren’t always accurate and may drift slightly over time. They do provide a starting point and indication of what kind of steam pressure you could be achieved when making coffee drinks.